Journal cover Journal topic
Annales Geophysicae An interactive open-access journal of the European Geosciences Union
Journal topic

Journal metrics

Journal metrics

  • IF value: 1.585 IF 1.585
  • IF 5-year value: 1.698 IF 5-year
    1.698
  • CiteScore value: 1.62 CiteScore
    1.62
  • SNIP value: 0.820 SNIP 0.820
  • IPP value: 1.52 IPP 1.52
  • SJR value: 0.781 SJR 0.781
  • Scimago H <br class='hide-on-tablet hide-on-mobile'>index value: 83 Scimago H
    index 83
  • h5-index value: 24 h5-index 24
Volume 17, issue 12
Ann. Geophys., 17, 1560-1573, 1999
https://doi.org/10.1007/s00585-999-1560-9
© European Geosciences Union 1999

Special issue: Equator S

Ann. Geophys., 17, 1560-1573, 1999
https://doi.org/10.1007/s00585-999-1560-9
© European Geosciences Union 1999

  31 Dec 1999

31 Dec 1999

Identification of magnetosheath mirror modes in Equator-S magnetic field data

E. A. Lucek1, M. W. Dunlop1, A. Balogh1, P. Cargill1, W. Baumjohann2, E. Georgescu2,4, G. Haerendel2, and G.-H. Fornacon3 E. A. Lucek et al.
  • 1The Blackett Laboratory, Imperial College, London SW7 2BZ, UK
  • E-mail: e.lucek@ic.ac.uk
  • 2Max-Planck Institute für extraterrestrische Physik, Garching, Germany
  • 3Institut für Geophysik und Meteorologie, Technische Universtät Braunschweig, Braunschweig, Germany
  • 4Institute of Space Sciences, Bucharest, Romania

Abstract. Between December 1997 and March 1998 Equator-S made a number of excursions into the dawn-side magnetosheath, over a range of local times between 6:00 and 10:40 LT. Clear mirror-like structures, characterised by compressive fluctuations in |B| on occasion lasting for up to 5 h, were observed during a significant fraction of these orbits. During most of these passes the satellite appeared to remain close to the magnetopause (within 1–2 Re), during sustained compressions of the magnetosphere, and so the characteristics of the mirror structures are used as a diagnostic of magnetosheath structure close to the magnetopause during these orbits. It is found that in the majority of cases mirror-like activity persists, undamped, to within a few minutes of the magnetopause, with no observable ramp in |B|, irrespective of the magnetic shear across the boundary. This suggests that any plasma depletion layer is typically of narrow extent or absent at the location of the satellite, at least during the subset of orbits containing strong magnetosheath mirror-mode signatures. Power spectra for the mirror signatures show predominately field aligned power, a well defined shoulder at around 3–10 x 10 –2 Hz and decreasing power at higher frequencies. On occasions the fluctuations are more sinusoidal, leading to peaked spectra instead of a shoulder. In all cases mirror structures are found to lie approximately parallel to the observed magnetopause boundary. There is some indication that the amplitude of the compressional fluctuations tends to be greater closer to the magnetopause. This has not been previously reported in the Earth's magnetosphere, but has been suggested in the case of other planets.

Key words. Magnetospheric physics (magnetosheath; plasma waves and instabilities; magnetopause, cusp and boundary layers)

Publications Copernicus
Special issue
Download
Citation
Share